Electronic equipment in the telecommunications industry, as well as other industries, is generally designed using a modular format. The modular subassemblies that make up an electronic assembly are generally housed in a chassis including multiple racks with modular compartments.
The modular design provides several advantages including reliability, ease of maintenance and economic savings. For example, if a module in the electronic assembly malfunctions, a service technician can remove and replace the malfunctioning module without taking the system employing the module out of service. If necessary, the malfunctioning module can then be repaired at a service location by specialized technicians familiar with that type of module. This permits field maintenance to be carried out by less skilled personnel and also results in a more reliable system.
The type of chassis to accommodate the modules vary depending on the environment where the equipment is located. For instance, U.S. patent application Ser. No. 09/069,368, entitled "Modular Power Supply Chassis Employing a Suspended Bus Bar Assembly," by Byrne, et al., commonly assigned with the present invention and incorporated herein by reference, discloses an open rack assembly that accommodates modules with an exterior cabinet enclosing the electronic equipment. Regardless of the chassis type and environmental factors, the electronic assembly provides the framework to deliver electrical power to or from the modules and provides electrical connectivity between the modules.
Various electrical conductor and connector arrangements have been configured to provide electrical connectivity between modules. Such arrangements include electrical wires bundled together or separate wires running from one location to another as well as other configurations. A common method to provide electrical connectivity between modules is to route the electrical conductors through conduits of the chassis support framework housing the modules.
A concern associated with the distribution of power in the modular system is minimizing the level of electromagnetic interference (EMI) emissions radiated from the system. In the case of electrical wiring being routed through the support members of the chassis framework, generally, the conduit includes apertures to allow for routing wires in and out of the conduit and to provide the necessary connections with the various electronic modules. The apertures, however, permit EMI emissions generated by high frequency switching within power modules to escape from the conduit that, unless controlled, may exceed agency limits and impair the performance of the surrounding electronics. Typically, the EMI emissions are minimized by high frequency filtering and by using gasketing material to cover the apertures. Filtering and EMI gasketing materials, however, are expensive and not preferred solutions to such problems.
Not only can the apertures permit an unacceptable level of radiated EMI emissions, the apertures may also weaken the structure supporting the conduit. If the conduit also serves as a support member of the chassis, additional support structure may be required. Generally, providing additional structural members to a chassis is undesirable because of the increased cost, space and weight considerations.
Another consideration associated with the control of radiated EMI emissions in the modular electronic assembly is the establishment of a low impedance connection that provides a common voltage potential between the chassis and the module case (such that gaps between the chassis and the module case are ineffective antennae for radiating EMI). Although the conductive module case can be coupled to the chassis with a separate wire or by other direct contact between the chassis and the module case, these approaches exhibit characteristic impedances that are too high to be effective for controlling EMI. Even in situations where a common voltage potential is established between the module case and the chassis by direct contact, the degree of design tolerance necessary to provide a common path for the modular case to the chassis generally increases total manufacturing cost and decreases reliability.
Accordingly, what is needed in the art is a device for use with a conduit employable in an electronic equipment chassis that establishes a common voltage potential between the chassis and the case of an electronic module to reduce EMI emissions associated with the electronic module.